Bou-Abdallah Fadi, Biasiotto Giorgio, Arosio Paolo, Chasteen N Dennis
Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, USA.
Biochemistry. 2004 Apr 13;43(14):4332-7. doi: 10.1021/bi0498813.
It is widely believed that the putative nucleation site (Glu61, Glu64, and Glu67) in mammalian H-chain ferritin plays an important role in mineral core formation in this protein. Studies of nucleation site variant A2 (E61A/E64A/E67A) of H-chain ferritin have traditionally shown impaired iron oxidation activity and mineralization. However, recent measurements have suggested that the previously observed impairment may be due to disruption of the ferroxidase site of the protein since Glu61 is a shared ligand of the ferroxidase and nucleation sites of the protein. This study employed a new nucleation site variant A1 (E64A/E67A) which retains the ferroxidase site ligand Glu61. The data (O(2) uptake, iron binding, and conventional and stopped-flow kinetics measurements) show that variant A1 retains a completely functional ferroxidase site and has iron oxidation and mineralization properties similar to those of the wild-type human H-chain protein. Thus, in contrast to previously published literature, this study demonstrates that the putative "nucleation site" does not play an important role in iron uptake or mineralization in H-chain ferritin.
人们普遍认为，哺乳动物重链铁蛋白中的假定成核位点（Glu61、Glu64和Glu67）在该蛋白的矿物核心形成中起重要作用。传统上，对重链铁蛋白成核位点变体A2（E61A/E64A/E67A）的研究表明其铁氧化活性和矿化能力受损。然而，最近的测量表明，先前观察到的损伤可能是由于该蛋白的铁氧化酶位点被破坏，因为Glu61是该蛋白铁氧化酶和成核位点的共享配体。本研究采用了一种新的成核位点变体A1（E64A/E67A），该变体保留了铁氧化酶位点配体Glu61。数据（氧气摄取、铁结合以及常规和停流动力学测量）表明，变体A1保留了完全功能性的铁氧化酶位点，并且具有与野生型人重链蛋白相似的铁氧化和矿化特性。因此，与先前发表的文献相反，本研究表明假定的“成核位点”在重链铁蛋白的铁摄取或矿化中并不起重要作用。
